Roger's SkyPix

Mini Cloud Atlas

Elevated Towering Cumulus

Elevated Towering Cumulus

These cloud towers formed in moist and unstable air mass rooted above the surface, hence the term "elevated." Since it was still early morning, the boundary layer (lowest layer of the troposphere, at and just above the surface) hadn't warmed up enough yet to remove the capping inversion and allow surface-based plumes of air to form their own convective towers. This activity instead was fueled by a layer of warm and moist air several thousand feet aloft which was much more unstable than the air at ground level. Although elevated convection usually is high-based, not all high-based convection is elevated! That's a common area of confusion. If air at the surface is part of the updraft, but the difference between temperature and dew point is large (as in a really hot day, or over much of the western U.S.), towers will be high-based but not elevated.

Also, if you know the direction of view, it's possible to diagnose important atmospheric processes from a photo like this. Here's how: Notice that the leaves are being blown toward the right (west), but the towers are tilted toward you and to the left (northeast). This means the wind is coming from the east at ground level, and from the southwest at cloud level. In the northern hemisphere, this clockwise changing of wind direction with height is a signal of warmer air moving into the area at low levels, and often accompanies or happens soon before rain or stormy conditions.

Norman OK (24 Apr 6) Looking S